This invention relates generally to medical devices and methods of using same. More particularly, the invention relates to devices, systems, and methods for altering a patient""s temperature and blood gas concentration levels, such as blood oxygen levels.
In many clinical conditions it is desirable to administer oxygen to a patient for the by purpose of increasing the partial pressure of oxygen within the patient""s blood. In certain conditions, implantable oxygenators may be employed to administer oxygen directly to a patient""s bloodstream. Examples of percutaneous oxygenators include those disclosed in U.S. Pat. Nos. 5,865,789; 5,501,663; 5,376,069; 5,219,326; 5,122,113; 4,986,809; and 4,911,689. The oxygenators disclosed in these references are connected to an inflow conduit that delivers oxygen through a plurality of generally tubular gas-permeable fibers. Oxygen diffuses outwardly through the fibers into the blood while carbon dioxide diffuses inwardly from the blood. A gas outflow conduit then caries any un-diffused oxygen and the carbon dioxide out of the body. At least some of the oxygenators disclosed in these references have attempted to reduce laminar streaming of blood flow around the oxygenators when they are inserted in a patient""s vascular system.
Some of these references also disclose warming of the oxygen prior to the delivery of the oxygen to the oxygenator in order to reduce the temperature difference between the patient""s blood and the oxygen flowing through the oxygenator. The reduction of the temperature difference acts to reduce condensation that may develop within the oxygenator.
Although the administration of oxygen may provide some benefit in terms of alleviating a patient""s symptoms, and helping preserve organ function, the metabolic state of the cells of the patient""s organ or organs may be normal or above normal, and thus, the use of oxygen alone to treat patients does not provide completely satisfactory results.
Mild hypothermia has been shown to reduce metabolic requirements of organs, such as the heart and/or the brain. Indeed, if the hypothermia is systemic, the metabolic demands of the entire body are generally reduced, so that the demands placed on the heart may be reduced. Additionally, when the patient""s body temperature is reduced and maintained 1xc2x0 C. or more below normothermic (e.g., less than 36xc2x0 C. in most individuals), such that the output of the heart increases, the condition and function of the heart muscle may improve significantly due to the combined effects of increased bloodflow to the heart, a temporarily decreased metabolic need and decreased metabolic waste products. Hypothermia may also provide protective effects on a patient""s organs by preventing undesirable spread of cellular death or injury.
One method for inducing hypothermia of the heart or entire body is through the use of a heat exchange catheter that is inserted into a blood vessel and used to cool blood flowing through that blood vessel. This method in general is described in U.S. Pat. No. 6,110,168 to Ginsburg, which is expressly incorporated herein by reference. Various heat exchange catheters useable for achieving the endovascular cooling are described in U.S. Pat. No. 5,486,208 (Ginsburg), PCT International Publication WO OO/10494 (Machold et al.), U.S. Pat. No. 6,264,679 (Keller et al.), PCT International Publication WO 01/58397, all of which are expressly incorporated herein by reference.
The potential for shivering is present whenever a patient is cooled below that patient""s shivering threshold, which in humans is generally about 35.5xc2x0 C. When inducing hypothermia below the shivering threshold, it is very important to avoid or limit the shivering response. The avoidance or limiting of the shivering response may be particularly important in patients who suffer from compromised cardiac function and/or metabolic irregularities. An anti-shivering treatment may be administered to prevent or deter shivering. Examples of effective anti-shivering treatments are described in U.S. Pat. No. 6,231,594 (Dae et al.).
Thus, there remains a need in the art for improving patient outcome and organ preservation in patients that suffer from compromised cardiac or respiratory functions.
The present invention provides a catheter device that is insertable into the vascular system of a human or veterinary patient. The catheter device of the invention generally comprises a) heat exchanger for controlling and adjusting the temperature of a patient, and b) a gas exchange element for delivering gas to the patient via the patient""s bloodstream.
An endovascular catheter device may comprise a catheter shaft, a heat exchanger, and a gas exchange element, each connected to the catheter shaft. The catheter shaft may have one or more internal lumens extending along the length of the shaft. The internal lumens are in fluid communication with the heat exchanger and the gas exchange element so that fluid, such as gas or liquid, may flow through the lumens and through the heat exchanger and gas exchange element.
The heat exchanger of the catheter device may be expandable. In certain embodiments of the invention, the heat exchanger may be a heat exchange balloon, and the balloon may comprise a plurality of lobes. The lobes of the balloon may be linearly, helically, or orthogonally disposed around the catheter shaft.
The gas exchange element of the catheter device may comprise a plurality of gas permeable fibers. The gas permeable fibers may be linearly, helically, and/or orthogonally arranged around the catheter shaft. The gas exchange element may be proximally disposed to the heat exchanger. In reference to the disclosure herein, the terms proximal and distal refer to the relative position on the catheter device. In other words, and as understood in the art, proximal refers to a position on the catheter device that would be closer to a physician""s hand when the device is being used in practice. Accordingly, distal refers to a position on the catheter device that is relatively farther away from the physician""s hand. By way of a specific example, a catheter device in accordance with the invention herein disclosed comprises a heat exchange element that is inserted into a patient""s body. Thus, the heat exchange element is distal to the portion of the catheter device that is disposed out of the patient""s body.
The foregoing catheter device may also comprise a flow disruption device, such as one or more fins or an expandable or inflatable pulsatile element. The flow disruption device may be connected to the catheter shaft and disposed along the length of the shaft to disrupt the laminar flow of blood around the catheter device as it flows around the gas exchange element or heat exchanger. In embodiments of the invention employing a pulsatile element as a flow disruption device, the pulsatile element may be disposed between the gas permeable fibers and the catheter shaft.
The catheter device may be provided as an element in a system for changing a patient""s temperature and/or delivering gas to a patient. The system may include one or more apparatus, which comprise a temperature regulator to deliver a heat exchange fluid to the heat exchanger of the catheter device, and a gas delivery regulator to deliver a gas to the gas exchange element of the catheter device. The control system may also comprise a controller to control the actions of the temperature and gas delivery regulator, a temperature monitoring device, and/or a cardiac monitoring device. The catheter device may also include one or more probes to monitor the patient""s temperature, blood gas concentration, and/or cardiac function.
The catheter device of the invention may be used to control a patient""s temperature and/or blood gas concentration. In one embodiment, the catheter device may be inserted into a patient""s vascular system, a heat exchange fluid may be urged through the heat exchanger, and a gas may be urged through the gas exchange element. The heat exchange fluid may cause a temperature change in the patient""s blood. The gas may permeate through one or more gas permeable fibers to be delivered to the blood. The method may also include one or more steps of disrupting the laminar flow of blood to enhance the temperature and gas exchange, and monitoring the patient""s temperature, and/or blood gas concentration levels.
The catheter device of the invention may further comprise a system including one or more controllers for automatically controlling the function of the device. The controller may receive a signal from, and be responsive to various sensors, for example, temperature sensors that sense a temperature of the patient and provide a temperature signal to the controller. In response to the sensed temperature, the controller may alter the function of the catheter device to increase or decrease the heat exchanged by the catheter by, for example, altering the temperature of the heat exchange fluid or increasing or decreasing the flow rate of the heat exchange fluid. Similarly, the system may comprise blood gas concentration sensors that provide a signal representing information concerning the blood gas status of the patient, in response to which, the controller may alter the functioning of the gas exchange portion of the catheter by, for example, altering the rate of gas flow, or the composition or concentration of gas flowing through the gas exchange catheter. The sensors may be independently placed on or in the patient, or may be incorporated into the catheter to sense parameters such as blood gases or temperature in the bloodstream.
The method of use of the catheter system may further comprise the step of controlling the thermoregulatory response of the patient. For example, if the temperature of the patient is reduced below the shivering threshold, an anti-shivering mechanism may be employed. Such anti-shivering mechanisms include warming blankets and various drug regimes, as disclosed herein.